There are drills like As and Bs and butt kicks and fast feet and I had a coach once that made us do strides holding a broomstick across our shoulders with our arms out like a big T to work on smooth legs without the upper body twisting around. The As are essentially high knees but you are better off actually seeing someone do the drills so that you have some reference since they are difficult to do from a written description. My advice would be to go to a high school near you (preferably one with a track coach that knows something about the sport) and ask if it would be ok for you to watch or take part in a workout. I coach track and have a few training partners that will occasionally come over and do workouts with the kids I coach.